Psychology the Nervous System

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Assignment 3

Written Essay Questions

1.
a) We are able to experience different types of sensations because our nervous system encodes messages. German physiologist Johannes Muller in his doctrine of specific nerve energies described a kind of code which is anatomical. In his doctrine, Muller explains that different sensory modalities exist because signals received by the sense organs stimulate different nerve pathways that lead to different areas of the brain. For example, when the ear receives signals, these signals cause impulses to travel along the auditory nerve to the auditory cortex. And signals from the eye cause impulses to travel along the optic nerve to the visual cortex. Because of these anatomical differences, light and sound produce different sensations.

b) The code in the nervous system that helps explain why a pinprick and kiss feel different is known as functional. These codes rely on the fact that sensory receptors and neurons fire or are inhibited from firing, only in the presence of specific kinds of stimuli. Functional encoding may occur all along a sensory route, starting in the sense organs and ending in the brain.

2. The lens of an eye operates differently from a camera, that just like a camera, the eye registers spots of light and dark, but neurons in the visual system build up a picture of the world by detecting meaningful features. The eye doesn’t passively record the external world, like a camera, ganglion cells and neurons in the thalamus of the brain respond to simple features in the environment, such as spots of light and dark. The existence of a specialized face module in the brain, explains why a person with brain damage may continue to recognize faces, after losing the ability to recognize other objects.

3. These units which were named after Alexander Graham Bell were called decibels (dB). Each decibel is 1/10 of a bel. Using decibels, they can be used to determine sound intensity, intensity of a wave’s pressure. Humans have an average absolute threshold of hearing of zero decibels and all decibels are not equally distant. For example, in my own environment, in my living room there is a 40decibel sound, my refrigerator and the light traffic from my window has about 50 decibels of sound. Everyday noises that may be hazardous to hearing could be rock concerts, deafening bars, stereos that are often played on full blast. In addition to that, noisy home appliances, lawn mowers and heavy city traffic also are hazardous to our ears.

4. If you were to inhale vapour from a rose, your receptors for smell have specialized neurons embedded in a tiny patch of mucous membrane in the upper part of the nasal passage. Millions of receptors in each nasal cavity respond to chemical molecules in the air. So when you inhale vapour from a rose, you’re pulling these molecules into the nasal cavity and can also enter from the mouth. These molecules then trigger responses in the receptors that produce that of fresh roses. From there, signals from the receptors are carried to the brain’s olfactory bulb by the olfactory nerve. And from the olfactory bulb, they travel to a higher region of the brain.

5. The basic concept of the gate- control theory, states the experience of pain depends on when pain impulses can get past a ‘’gate’’ in the spinal cord. The gate is a pattern of neural activity that blocks pain messages coming from the skin, muscles and internal organs or lets those signals through. Most of the time this gate is kept shut by impulses coming into the spinal cord from large fibres that respond to pressure or by signals coming down from the brain itself. However, when body tissue is injured, the large fibres are damaged and the smaller fibres open the gate. Once the gate is open, pain messages reach the brain unchecked. However, the theory doesn’t explain phantom pain, the pain from an amputated limb or organ that a person continues to feel after surgery. Melzack explains, even...
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